Q.How do I go about changing the Serpentine Belt and, if necessary, the A/C belt on my 2000 BMW 740iL?

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A. First thing you have to do is take off the fan and fan coupling.

Layout of Serpentine Belt

Then loosen nuts (1) and (2), loosen and remove the Serpentine Belt.

Use hex head (1) to preload adjusting plate to end of long bore (2) and tighten nuts (3). Installation:
Fit Serpentine Belt and check it is correctly located on pulleys.

The A/C belt is as easy as it looks. Just loosen the tensioner and replace the belt.

See also:
- How to tell if you have mechanical or hydraulic belt tensioners (1) & how to switch from mechanical to hydraulic (1) and what is the difference between the two types (1) (2) & how to rebuild your hydraulic tensioners (1)